The two-way coupling model was adopted to study the two-dimensional gas-solid mixing layer. The flow was simulated by pseudo-spectral method and particles were traced with Lagrangian method. It is found that the concentration and the Stokes number of the particles have distinct effect on the flow not only accounting for the influence of the flow on the particles, but also the particles' counteraction on the flow. The particles accelerate the dispersion of the vorticity and inhibit the variance of the flow and diminish the intensity of the coherent structure. The lifetime of the vortex is shortened. The pattern of particles' distribution is similar to the results from one-way coupling model.